1. Field of the Invention
The present invention relates to a system for achieving cell diagnosis of continuity in a cell exchange, for example, a system for achieving cell diagnosis of continuity suitable for application to a speech path (SP) side apparatus in for example a broad band asynchronous transfer mode (ATM) cell exchange.
An ATM cell exchange individually adds designation information (header information) to fixed length packets referred to as "cells" and performs switching processing by having these cells perform self routing. In recent years, there has been a growing demand for broad band ATM cell exchanges of the order of a few hundreds Mbps or more so as to handle multimedia transmissions.
Such an ATM cell exchange performs self-diagnosis in order to ensure the normality of this ATM cell exchange itself. This self diagnosis is mainly carried out by using microprocessors mounted for every functional block of this ATM cell exchange and detecting existence of hardware failures.
However, it is difficult to ensure normality with a further higher reliability by only this self diagnosis. For this reason, it is required to check for the occurrence of abnormalities such as loss of cells or duplication of cells by actually sending cells into the ATM cell exchange, particularly into the SP side apparatus. The diagnosis for this check is called the "cell diagnosis of continuity". The present invention will describe a method for cell diagnosis of continuity for achieving this.
2. Description of the Related Art
As will be explained in detail later by referring to the drawings, a cell exchange, for example, a broad band ATM cell exchange, is roughly comprised of three types of functional blocks. Namely, it is comprised of a switching part, a common part, and individual parts. Usually a plurality of individual parts (1 to n) are mounted, each of which individual parts functions as an interface with several thousands of subscriber terminals connected under it. A plurality of path routes are set among the switching part, common part, and individual parts through which communication is carried out among a plurality of subscriber terminals.
The means for the above mentioned cell diagnosis of continuity most relevant to the present invention is a cell test equipment explained in detail later. This cell test equipment sends testing cells to predetermined path routes, receives the sent cells, and checks whether or not these cells are normally received. An actual example of this cell testing equipment is a broadband test unit (BTSU).
As will be explained in detail later, a conventional cell testing equipment (BTSU) has a maximum cell feeding speed of for example 156 Mbps. It cannot send testing cells with a cell feeding speed more than this.
In recent years, however, the maximum operating band width of the individual parts has been broadened considerably to deal with the new multimedia age. For example, the maximum operating band width has been broadened so as to increase the speeds handled from the conventional 156 Mbps to 622 Mbps.
This means that the above conventional cell test equipment can no longer perform cell diagnosis of continuity in a broad band ATM cell exchange. In this case, one could conceivably develop a new cell test equipment capable of handling 622 Mbps to enable diagnosis.
However, it was found that considerable technical difficulties were involved in the development of practical cell test equipment able to handle 622 Mbps speeds.